More particularly, the invention relates to a track assembly for the seat of a vehicle, comprising:                first and second parallel tracks extending along a longitudinal direction and each comprising an adjustment mechanism,        an electric motor adapted for driving the mechanisms for adjusting said tracks and connected to said adjustment mechanisms via flexible connections,        at least one support member extending along a transversal direction substantially perpendicular to the longitudinal direction and connecting the motor to at least one of first and second tracks, said support member comprising at least one guide adapted for retaining the flexible connection, and fully surrounding flexible connection over at least one portion of its length.        
Moreover, the invention further relates to a seat of a vehicle provided with such a track assembly.
Finally, the invention further relates to a support member for such a track assembly.
FR-A-2 883 810 describes an example of such a track assembly.
In the known track assemblies of this type, the support member is a cross member which is fixed at its two ends on the two tracks and which comprises guides in the form of retaining clips of the flexible connections.
Also known in U.S. Pat. No. 6,021,990 is an adjustment mechanism comprising an electric motor and support members which are based on a transverse bar which connects the two tracks.
These known track assemblies provide complete satisfaction. It has however appeared useful to further perfect them, in particular to simplify the mounting.